During the 1950's some fats were prepared by substituting acetic acid for a portion of the fatty acids occurring in ordinary fats or oils, thus producing what were then named "acetoglycerides" (Feuge, R. O., Food Technology 9: 314-318 (1955)). Feeding studies indicated that the nutritive value of mono- and diacetin fats were essentially the same to animals as those fed the corresponding conventional triglycerides (Mattson, F. H., et al., J. Nutr. 59: 277-285 (1956)).
Acetostearins are waxy fats having high, sharp melting points, limiting their applications in food products. One study described the fats as "highly flexible" and elastic; at a temperature of 22.degree. C., they could be stretched more than 800% (Feuge, R. O., et al., J. Amer. Oil Chem. Soc. 29: 11-14 (1952)). When chewed in the mouth, diacetostearin has been described as "somewhat like a gum" (U.S. Pat. No. 2,615,160 to Baur, column 7, line 55). Though initially suggested for a variety of edible products, including coatings and possibly chocolate coatings, as well as in icings and frostings, as spray oils for crackers, as edible "beeswax" for synthetic honey, as an edible chewing gum base, and as protective coatings for products such as fruits, cheese, preserves, and meats (U.S. Pat. No. 2,615,160 to Baur, column 7, lines 59 to 64), the disclosures did not provide products with the functionality required for quality confectionery fats.
The diacetostearin of U.S. Pat. No. 2,615,160 is waxy and rubbery, so it is unacceptable for use as a confectionery coating, and acetodistearin tends to bloom and is also waxy. Instead of stretching, quality confectionery coatings and chocolates should have snap. Quality confectionery coatings also melt in the mouth without waxiness and preferably exhibit some glossiness. Preferred confectionery products contract on cooling to facilitate demolding. Dull, waxy diacetosterins are difficult to demold and so they do not exhibit these desirable properties.
Thus, in the intervening decades, waxy acetoglycerides have been primarily used, not as confectionery fats, but as protective coatings, thin films, moisture barriers and plasticizers. Some compositions of this nature are referred to as "hot melts" and may contain antibiotics (U.S. Pat. No. 3,192,057 to Hines and Shirk) or polymeric materials (U.S. Pat. No. 3,388,085 to Levkoff and Phillips) to prolong the life of the coating.
Recent research in this laboratory has shown that acetoglycerides bearing long (C.sub.16 to C.sub.24), saturated pendant groups such as the acetostearins are low in calories (U.S. application Ser. No. 07/804,140, cited above). Therefore, it would be desirable to have crystal modifiers that modulate the waxy, rubbery properties of acetoglycerides, especially diacetostearin, so that these fats can be employed in confectionery coatings.